Image: False color image of Popocatépetl seen on April 23, 2012. Inset is an image of the ash plume from the volcano seen on April 16, 2012. Images courtesy of the NASA Earth Observatory.

Villarrica and Quetrupillan, Chile

It is always nice to get a two-for-the-price-of-one and in this false-color February 2003 shot, both Villarrica and nearby Quetrupillan show up prominently. Villarrica is a much more active volcano than Quetrupillan and in this image, the lava lake at the summit appears in red. The lava lake at Villarrica is still there, 9 years later - in fact, the volcano has been more active over the last few months, with small ash plumes and spattering from the lava lake. Quetrupillan, on the other hand, hasn't had an eruption since 1872 (which is also the only known historical eruption from the volcano).

Image: False color ASTER image of Villarrica and Quetrupillan taken on February 13, 2003. Image courtesy of the NASA Earth Observatory.

Puyehue-Cordón Caulle, Chile

After nearly a year of activity, the eruption at Puyehue-Cordón Caulle seems to be over. No ash emissions have been spotted over the past few weeks and SERNAGEOMIN has lowered the alert status at the yellow after the ash ended and seismicity continues its downward trend, although the crater area has some noticeable incandescence at night. The lack of ash-and-steam plumes means we can get a view of the area around the volcano and where the deposits from the eruption has affected. Once you see the image (see above), you realize that it isn't even the zone adjacent to the volcano, but rather the ash spreads hundreds of kilometers to the east across Argentina. Some of this ash might make its way into the geologic record, but much of it is so thin that the ash will be washed away by surface processes. It just shows that even what seems like a large eruption might not leave a long-lasting widespread geologic legacy.

Image: April 12, 2012 MODIS image of the Chile and Argentina including Puyehue-Cordón Caulle. Image courtesy of the NASA Earth Observatory.

Nevado del Ruiz, Colombia

The elevated signs of activity continue at Colombia's Nevado del Ruiz with plumes reaching 900 meters above the crater and increased sulfur dioxide continues from the volcano. This image of Ruiz from 2010 shows the real threat from the volcano - the abundant snow and ice around the Arenas crater (the center of current activity) means lahars are likely the #1 volcanic hazard. El Tiempo has a report about farmers who live in the area around the volcano and they express concerns that sound familiar to many who see these volcanic crises unfold: "who will make sure my property and animals are safe without me?" These concerns could cause residents to lose valuable time when they need to evacuate.

Image: An image of Nevado del Ruiz in Colombia seen on April 23, 2010. Image courtesy of the NASA Earth Observatory.

Valley of 10,000 Smokes, Alaska

2012 marks the 100th anniversary of the largest eruption of the 20th century - the June 1912 eruption Novarupta in Alaska. The eruption actually involved multiple volcanoes, with eruption from Novarupta, a new volcano vent formed during the 1912 eruption that prompted the collapse of nearby Katmai. The eruption formed the famous Valley of 10,000 Smokes, where the pyroclastic flow deposit spilled to the northwest and southeast. The name comes from the abundant plumes of steam that came from the deposits years after the material was deposit as the heat and gases in the deposit escaped. The image above was taken in 1994, over 82 years after the eruption, and it is remarkable how much volcanic debris is still moving through the rivers in the area - look for more on the Valley of 10,000 Smokes anniversary later this spring.

Image: The Valley of 10,000 Smokes in Alaska seen in September 1994. Image courtesy of the NASA Earth Observatory.

Image: Shiveluch and Kliuchevskoi seen on April 15, 2012. Image courtesy of the NASA Earth Observatory.

Tambora, Indonesia

This International Space Station (ISS) image of the Tambora caldera in Indonesia just shows how impressive of a volcanic feature it is. The caldera is 6 kilometers across and the product of the 1815 eruption of Tambora. The volcano was rumbling towards the end of 2011, prompting an elevation of the alert status, but recently the alert status was lowered back to Green, meaning the activity was at background levels. This doesn't mean there isn't activity across Indonesia as this week saw activity at Lokon-Empung and Lamongan.